After they uncharacteristically allowed 129 rushing yards in their season-opening win over the Cincinnati Bengals, stopping the run seemed to be the biggest concern for the Ravens defense.

But the Ravens have spent the last three weeks watching footballs whiz past their ears and into the arms of receivers. Only three teams have been victimized for more passing yards than the Ravens, who rank 23rd in the NFL in total defense. But while those struggles against the pass remain a primary concern, the Ravens have quietly gotten back to smothering running backs.

"It's nothing really schematic. We're playing the same defense we've played," coach John Harbaugh said. "Our guys up front have just tightened it up a little bit. We're playing the kind of technique that we want to play up front. Our linebackers are fitting in well with the defensive line, and we are getting great support from our secondary. It's just good, basic football."

In their last three games, the Ravens allowed opponents to gain just 2.7 yards per carry, which partially explains why teams have resorted to exploiting them through the air. But Sunday at Arrowhead Stadium, Jamaal Charles and the Kansas City Chiefs, who rank first in the NFL in rushing, hope to seriously test the notion that the Ravens have tightened up in the trenches.

Ravens players say they have learned from mistakes made in the Cincinnati game, particularly from a first half in which they struggled to slow down BenJarvus Green-Ellis. At times players were impatient and over aggressive —as Paul Kruger put it, shooting their gun too early — and lost focus on their assignment, pursuing the back instead of plugging the proper running lane.

The following week, the Ravens were much more disciplined. They missed at least 10 tackles, but they swarmed Philadelphia Eagles running back LeSean McCoy before he could break free to the outside. McCoy ran for 81 yards and a touchdown on 25 carries — a 3.2 yardaverage per carry. In his three other games, he averaged 5.4 yards per carry while rushing for 303 yards.

A week after that 24-23 loss, Stevan Ridley and the New England Patriots, who like the Eagles also rank in the top eight in rushing offense, mustered 77 yards on 34 carries in a Ravens win.

"Our front seven is really starting to get back to form," linebacker Ray Lewis said.

Limiting the damage done by Charles, who averages a 5.8 yards per carry, would be further evidence of that, and the Chiefs also have running backs Shaun Draughn and Peyton Hillis, who could miss Sunday's game with ankle injury, as a physical change of pace from Charles. But as Harbaugh explained, Charles is "the straw that stirs the drink."

A year removed from a left knee injury that ended his 2011 season after five quarters, Charles has sprinted to 415 rushing yards — impressive considering the Chiefs have yet to hold a lead this season — on 72 carries while adding a pair of meandering touchdown runs to his highlight reel.

Charles got just 22 carries in the first two weeks, but in Week 3, he rushed for 233 yards and a touchdown while also catching six passes for 55 yards as the Chiefs erased an 18-point deficit before beating the New Orleans Saints in overtime. A week later, he rushed for 92 yards and a touchdown — and added a receiving touchdown — in a 17-point loss to the San Diego Chargers.

"Obviously, last year with the injury, the guy is coming out to prove he's an elite back in this league again," said running back Ray Rice, who was drafted a round before Charles in 2008.

As the Ravens prepare for the Chiefs, Harbaugh's staff has cued up Charles' 91-yard touchdown run against the Saints to hammer home a coaching point about the need to set the edge and funnel Charles, a dangerous runner in the open field, back into the teeth of the Ravens defense.

After taking a handoff from embattled quarterback Matt Cassel on that play, Charles ran to his left, patiently looking for a seam in the Chiefs' zone-blocking scheme. He found one outside of left tackle Branden Albert (Glen Burnie H.S.) then showed off his greatest asset while racing past the Saints.

"Straight speed, man," said Lewis, who leads the Ravens with 33 tackles. "[He's] one of those guys that are home run hitters. If you let him get in the open field -- you saw it last week against the [New Orleans] Saints -- you jump out of a gap here or there, one seam, and he's out of the gate. We saw this guy before, we've played him before, and we know what we're up [against]."

The last time they saw him in a meaningful game was the AFC wild card round after the 2010 season. Charles rushed for 82 yards on nine carries and his 41-yard touchdown run gave the Chiefs an early lead, but the Ravens knocked him out of the game as they rolled to a 30-7 win.

But the Ravens, who have ranked in the top five in run defense every season since 2006, look a lot different defensively than they did two seasons ago. In some ways, they don't even resemble the stout unit from the 2011 season, and it goes beyond their struggles against the pass.

Reliable run defenders Jarret Johnson and Cory Redding are gone, and Terrell Suggs is sidelined as he rehabs his surgically-repaired Achilles tendon. The Ravens have four new starters in their front seven, another reason why Ravens players feel their run defense, currently ranked 13th in the league, will continue to improve going forward.

"Even though there is new faces in the defense, as every week and every game goes by, everybody gets comfortable with who they are playing with," new starting nose tackle Ma'ake Kemoeatu said. "It's been good, but [the Chiefs] will be a good test for our run defense."